The investor class is simply insatiable and you can't just satisfy the demand because it's always growing beyond all reason.
You need to curb investors interest in real estate.
So basically ban buying residential real estate on credit. That's a start.
It would have interesting sideffects. One of them would showing clearly to the masses how unaffordable houses actually already are. Unfortunately rents would go up in the short term from increased demand from people who'd otherwise get a loan. So the rich people would keep buying them raising the prices till the new equilibrium is reached.
Eventually rents would settle at how much people who rent can pay without starving and house prices would settle at whatever's the price of whatever asset that yields similar returns.
I don't think it would be at 10% of today's prices